Let →a,→b,→c be three vectors such that →a≠0 and |→a∣=∣→c∣=1,∣b∣=4 and |→b×→c∣=√15 , if →b−2→c=λ→a, then λ equals to

Let →a,→b,→c be three vectors such that →a≠0 and |→a∣=�

1.	Let →a,→b,→c be three vectors such that →a≠0 and \|→a∣=∣→c∣=1,∣b∣=4 and \|→b×→c∣=√15 , if →b−2→c=λ→a, then λ equals to
Answer» Let $\to a, \to b, \to c$ be three vectors such that $\to a \neq 0$ and $\| \to a ∣=∣ \to c ∣= 1, ∣ b ∣= 4$ and $\| \to b \times \to c ∣= \sqrt{15}$ , if $\to b - 2 \to c = λ \to a$ , then $λ$ equals to